MTOR and osteoporosis: Remarkably, the multiple bioactivities of monotropein, such as anti-osteoporosis, anti-oxidation, anti-inflammation, anti-nociception, and hepatic or renal protection, are closely associated with its capability of attenuating the activation of Nrf2/HO-1 signaling pathway, inhibiting MAPK signaling pathway, downregulating the NF-κB signaling pathway, and regulating the mTOR and autophagy signaling pathway.